1. Field
The present invention relates to a battery management system. More particularly, the present invention relates to a battery management system used in a vehicle using electrical energy, and a driving method thereof.
2. Description of the Related Art
A vehicle using an internal combustion engine using gasoline or heavy oil as a main fuel has a serious influence on the generation of environmental pollution such as air pollution. In recent years, much effort has been made to develop an electric vehicle or a hybrid vehicle so as to reduce the generation of environmental pollution.
The electric vehicle refers to a vehicle using a battery engine that operates by an electrical energy output from a battery. The electric vehicle uses a battery in which a plurality of rechargeable secondary cells are provided as one pack as its main power source. Thus, the electric vehicle has advantages in that there is no discharge gas and a noise is very small.
The hybrid vehicle refers to an intermediary vehicle between the vehicle using an internal combustion engine and the electric vehicle. The hybrid vehicle uses two or more power sources, for example, an internal combustion engine and a battery engine. At present, the hybrid vehicle based on a hybrid type using an internal combustion engine and a fuel cell for continuously supplying hydrogen and oxygen while inducing a chemical reaction to directly obtain electrical energy or using a battery and a fuel cell is being developed.
In the vehicle using the battery engine, the number of secondary cells is gradually increasing, and a battery management system (BMS) needs a cell balancing control method for efficiently managing a plurality of connected cells for improvement of the power source.
Particularly, if a reference time is greater than an unchecked time after key-off, upon key-on, an open circuit voltage (OCV) is measured, and an initial state of charge (SOC) is estimated using a table of the SOC and the OCV. The SOC of the battery is estimated in a method in which a measured electric current is added to an electric current associated with the estimated initial SOC.
The table of the OCV and the SOC has experimental data measured through experiments under various conditions of a temperature, a current, a voltage, and a fatigue state of the battery, and is stored in a micro control unit (MCU) of the BMS. However, having a limited memory, the MCU may be overloaded since it stores the table of the OCV and the SOC obtained through measurement under the various conditions. Accordingly, it is required to distinguish a region based on a relationship of the OCV and the SOC, and differently set an initial SOC estimating method correspondingly to the distinguished region.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.